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Why Does Insomnia Cause Weight Gain? 7 Reasons

by Dale Cudmore | Updated: Feb 20, 2022

One of the most common side effects of insomnia is weight gain.

It’s actually worse than it sounds, because obesity is one of the biggest risk factors for insomnia.

In other words, gaining weight as a result of sleep problems, can lead to even worse sleep problems (which then leads to more weight gain, and so on). It’s a vicious negative cycle.

We’re going to take a quick look at the science behind why insomnia causes many people to gain weight.

The 7 Main Reasons Insomnia Causes Weight Gain

I’ve grouped the main effects of insomnia that could lead to weight gain into 7 main categories.

Some of them come from a proposed model linking sleep deprivation and obesity from a systematic review (1):

Some of these reasons have more evidence behind them than others, and not all will apply for everyone with sleep issues.

Insomnia Causes Increased Appetite

Studies looking at partial sleep deprivation have found that it causes an increase in hunger and appetite (2). With 2 days of sleep restrictions:

Hunger increased by 25%, appetite increased by 23%, with a preference for calorie-dense foods with high carbohydrate content.

It turns out that sleep restriction causes:

  • Increased ghrelin (the “hunger” hormone) levels
  • Decreased leptin (the “I’m full” hormone) levels

Those key hormones are the two main ones that affect appetite.

Less Sleep Gives More Opportunity to Eat

There’s less research behind this, but it has been suggested by some, and it’s fairly common sense (3).

If you’re awake for more time, most people are more likely to eat more.

This does depend on the individual, and even their culture and habits.

For example, I grew up in an environment where eating was common while watching TV, so if I was up for longer doing things like watching TV, I would eat more.

Insomnia Leads to More Fatigue

It’s quite obvious that sleeping less for long periods of time makes you generally feel fatigued. Still, research has confirmed this effect (4).

The issue here is that fatigue leads to less physical activity, which then leads to a caloric surplus and weight gain.

Studies on men, women, and children have all found that short sleep is linked to reduced physical activity (5).

Insomnia Increases Stress Levels

One of the most impactful side effects of insomnia is that levels of cortisol increase, especially later in the day (6).

So by the time you’re done with work or school, someone with insomnia is more stressed than someone who sleeps well.

When someone is stressed, they make worse decisions. Many people stress eat junk food, or seek some other form of instant relief instead of doing something “hard” like exercising.

In addition, stress has many other detrimental effects on the body.

For example, elevated cortisol reduces growth hormone production, which can lead to muscle mass loss.

Mood Swings and Irritability

There is a strong link between insomnia and mood disorders like depression. Either one can cause the other, and it’s a vicious cycle on its own.

There’s evidence that insomnia worsens mood and makes people more irritable (7). This is related to stress as well as we’ve already covered.

For similar reasons, you’re less likely to make your best decisions when it comes to how you spend your time if you are moody or even showing signs of depression.

Headaches and Concentration Issues Are Common In Insomniacs

There’s good evidence that shows that insomnia can cause headaches.

One study with 50 insomnia patients found that (8):

Headache was reported by 48% of insomnia patients

That’s a symptom that I frequently had when I used to have sleep issues.

If you have a headache, it’s hard to concentrate on pretty much anything. Anything that requires sustained effort like work, exercise, or cooking a healthy meal becomes a lot more difficult.

Depending on the person, this can lead to less exercise and a poorer diet, which can lead to weight gain.

Lower Testosterone Levels

While this is more of an issue for males, testosterone is still important for females.

One study of over 1,000 men found that less sleep correlated with less testosterone (9).

While testosterone isn’t the primary driver of energy levels, it certainly does contribute to it.

In addition, a testosterone deficiency can lead to inflammation, slower recovery from physical activity, and many other effects that may indirectly affect activity levels.

How to Prevent Weight Gain From Sleep Problems

Not all people with insomnia gain weight.

Some react differently than most people, and some people have a lot of will power and discipline, and will continue to eat well and exercise.

However, that’s very difficult, and not everyone will be able to do that.

Primarily, the sleep issues need to be fixed first as much as possible.

See our guide to insomnia treatment if you’d like to learn more about how sleep issues are typically addressed.

In many cases, seeing a doctor to get help is crucial to solving the sleep issues and minimizing weight gain. After sleep issues are resolved, any weight gain can be addressed with diet and exercise.


  1. Short Sleep Duration and Weight Gain: A Systematic Review
  2. Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite
  3. Sleeping more as a way to lose weight
  4. Cumulative sleepiness, mood disturbance, and psychomotor vigilance performance decrements during a week of sleep restricted
  5. Association between reduced sleep and weight gain in women, Reduced risk for overweight and obesity in children by duration of sleep
  6. Recurrent short sleep, chronic insomnia symptoms and salivary cortisol
  7. Treatment of insomnia in patients with mood disorders
  8. Headache characteristics in obstructive sleep apnea syndrome and insomnia
  9. Sleep Duration and Disturbances Were Associated With Testosterone Level, Muscle Mass, and Muscle Strength

Medical Disclaimer: The information on is not intended to be a substitute for physician or other qualified care. We simply aim to inform people struggling with sleep issues about the nature of their condition and/or prescribed treatment.

About the authorDale is the founder of Snooze University and a sleep researcher. I overcame my sleep issues and now I'd like to help you do the same by summarizing the latest sleep studies for you.